Green hydrogen may play a key role as an energy carrier in the future. However, due to its low volumetric energy density (1.3 kWh/l at 700 bar and 20°C) compared to fossil fuels like gasoline (8.8 kWh/l), optimizing the use of space for hydrogen tanks is essential. However, conventionally wound pressure vessels are very inflexible in terms of their geometric dimensions. Additionally, any change in geometry requires the redesign of the liner (a barrier in the pressure vessel to prevent hydrogen permeation and manufacturing support). Therefore, a new design of cylindrical pressure vessels was developed and patented at IVW, where both the length and diameter can be chosen almost arbitrarily. The new developed design is made of purely axial and circumferential oriented carbon fibre reinforced plastic (CFRP) layers. The loads in the pressure vessel are transferred layer by layer to a metallic dome. This layer wise load transfer leads to a uniform load introduction to the metallic dome.
Due to the mandatory winding angle, it is not readily possible to apply purely axial fiber layers by traditional winding process. Also, pressure vessels with a diameter smaller than approximately 200 mm cannot be manufactured in a production-ready process, as the winding angle deviates significantly from the geodesic path, and the domed area disproportionately thickens due to frequent winding around a small area. Therefore, next to the design of the pressure vessel a novel production process has been developed which makes it possible to produce pressure vessels with a very small diameter and purely axial and circumferential fibre orientation. The new production process is based on a winding star that enables the axial layers to be placed. Several pressure vessels have been produced and burst pressure tests have been performed. During those tests, a burst pressure of more than 1575 bar has been achieved.